GotoItemByIndex Method

C#
Visual Basic
Objective-C
Java

public virtual void GotoItemByIndex( 
   int index
)

'Declaration

Public Overridable Sub GotoItemByIndex( _
   ByVal index As Integer _
)

Parameters

index: The 0-based index of the item

To go to an item, use GotoItem, to go to an item by its index, use GotoItemByIndex.

The "GoTo" methods scrolls the viewer so the top-left portion of the item is visible in the current control boundary without changing the other transformation properties.

To ensure that an item is visible, use EnsureItemVisible, to ensure an item is visible giving its index, use EnsureItemVisibleByIndex.

The "Ensure" methods scrolls the viewer the minimum required to ensure the item is fully visible in the current control boundary without changing the other transformation property. If the item is already fully visible, then nothing happens. If the item is larger than the current control boundary, then the viewer will scrolls the minimum amount required where any of the edges (top-left, top-right, bottom-left or bottom-right) is visible.

For more information refer to Image Viewer Layouts, Image Viewer Appearance, Image Viewer Items, Image Viewer Transformation, and Image Viewer Bounds and Transform.

This example will add a few items to the viewer and then allows the user to go to an item.

Run the demo and click the Example button.

Start with the ImageViewer example, remove all the code inside the example function (search for the "// TODO: add example code here" comment) and insert the following code:

C#
Visual Basic
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Copy Code

Imports Leadtools
Imports Leadtools.Controls
Imports Leadtools.Codecs
Imports Leadtools.Drawing
Imports Leadtools.ImageProcessing
Imports Leadtools.ImageProcessing.Color

' Clear all the images already the viewer
_imageViewer.Items.Clear()
' Use vertical view layout
_imageViewer.ViewLayout = New ImageViewerVerticalViewLayout()
' Make sure the item size is larger than the image size (thumbnails mode)
_imageViewer.ItemSize = LeadSize.Create(200, 200)
_imageViewer.ItemPadding = New Padding(8, 8, 8, 20)
_imageViewer.ImageBorderThickness = 1
' Add 4 items to the viewer
Using codecs As New RasterCodecs()
   For page As Integer = 1 To 4
      Dim item As New ImageViewerItem()
      Dim fileName As String = Path.Combine(ImagesPath.Path, String.Format("ocr{0}.tif", page))

      ' Create a thumbnail from the image
      Using image As RasterImage = codecs.Load(fileName, page)
         item.Image = image.CreateThumbnail(180, 180, 24, RasterViewPerspective.TopLeft, RasterSizeFlags.Resample)
      End Using

      item.Text = String.Format("Item {0}", page - 1)
      _imageViewer.Items.Add(item)
   Next page
End Using

' Add a combobox control to show the items
Dim comboBox As New ComboBox()
comboBox.Top = _label.Bottom
_label.Parent.Controls.Add(comboBox)

' Add an entry for each item to the combo box
For Each item As ImageViewerItem In _imageViewer.Items
   comboBox.Items.Add(item.Text)
Next item

' When the user selects an item from the combo box ...
AddHandler comboBox.SelectedIndexChanged,
Sub(sender, e)
   ' Get the corresponding item index...
   Dim index As Integer = comboBox.SelectedIndex
   ' And go to it
   _imageViewer.GotoItemByIndex(index)

using Leadtools;
using Leadtools.Controls;
using Leadtools.Codecs;
using Leadtools.Drawing;
using Leadtools.ImageProcessing;
using Leadtools.ImageProcessing.Color;

// Clear all the images already the viewer
_imageViewer.Items.Clear();
// Use vertical view layout
_imageViewer.ViewLayout = new ImageViewerVerticalViewLayout();
// Make sure the item size is larger than the image size (thumbnails mode)
_imageViewer.ItemSize = LeadSize.Create(200, 200);
_imageViewer.ItemPadding = new Padding(8, 8, 8, 20);
_imageViewer.ImageBorderThickness = 1;
// Add 4 items to the viewer
using (var codecs = new RasterCodecs())
{
   for (var page = 1; page <= 4; page++)
   {
      var item = new ImageViewerItem();
      var fileName = Path.Combine(ImagesPath.Path, string.Format("ocr{0}.tif", page));

      // Create a thumbnail from the image
      using (var image = codecs.Load(fileName, page))
      {
         item.Image = image.CreateThumbnail(180, 180, 24, RasterViewPerspective.TopLeft, RasterSizeFlags.Resample);
      }

      item.Text = string.Format("Item {0}", page - 1);
      _imageViewer.Items.Add(item);
   }
}

// Add a combobox control to show the items
var comboBox = new ComboBox();
comboBox.Top = _label.Bottom;
if (_label.Parent != null)
{
   _label.Parent.Controls.Add(comboBox);
}

// Add an entry for each item to the combo box
foreach (var item in _imageViewer.Items)
   comboBox.Items.Add(item.Text);

// When the user selects an item from the combo box ...
comboBox.SelectedIndexChanged += (sender, e) =>
{
   // Get the corresponding item index...
   var index = comboBox.SelectedIndex;
   // And go to it
   _imageViewer.GotoItemByIndex(index);
};

Target Platforms

Reference

ImageViewer Class
ImageViewer Members